说明：  编译环境为PB,或AK,实现27x平台上对DMA的控制,由于270平台上DMA都处在同一个一级中断下,要使用单个的DMA通道,通常也可以在OAL重新映射其中断号,但比较费事,本驱动实现对DMA的管理,用户可以申请各个优先级的通道
(build environment for PB, or AK, achieving 27x platform for DMA control As the 270 platform with DMA are in the midst of an interruption of a, to use a single DMA channels, normally qualify can also re-mapping in its interruption, but for this comparison, the DMA-driven to achieve the right management, Users can apply for various priority access)